160 SEXES. 



190. The pollen consists of exceedingly minute hollow 

 balls, or cases, containing myriads of moving particles, which 

 are the fertilising principle of the stamens. 



191. The pistillum has at its base one or more cavities or 

 tells, in which hodies called ovulate placed; and at its apex 

 one or more secreting surfaces called stigmata. 



192. The ovula are the rudiments of seeds. 



193 If the fertilising powder of the pollen come in contact 

 with the stigma, the ovula in the cells of the pistillum are 

 vivified, and become seeds. 



194. But if this contact does not take place the ovula cannot 

 possibly be vivified, but shrivel up and perish. 



195- The phenomenon of vivification takes place in conse- 

 quence of the descent of a portion of the moving panicles (190.) 

 of the pollen into the ovula, where such particles form the 

 commencement of future plants. 



196. In wild plants a stigma is usually acted upon only by 

 the pollen of the stamens which belong to it. 



197. In this case the seeds thus vivified will, when sown, 

 produce new individuals, differing very little from that by 

 which they were themselves produced. 



108. And, therefore, wild plants are for the most part multi- 

 plied from generation to generation without change. 



199. But it is possible to cause deviations from this law, by 

 artificial means. 



200. If the pollen of one species is placed upon the stigma, 

 of another spec ; es, the ovula will be vivified; and what is 

 called a hybnd plant will be produced, by those ovula when 

 they shall have grown to be seeds. 



201. Hybrid plants are different from both their parents, 

 and are generally intermediate in character between them. 



202. ^hey have little power of perpetuating themselves by 

 seeds; but they may if woody be perpetuated by cuttings 

 (312.), buds (354.) scions (335.), &c. 



203. Therefore, no hybrids but such as are of a w r oody 

 perennial character can be perpetuated. 



204. It usually happens that the hybrid has the constitution 

 and general aspect of the poliiniferous parent ; but is in- 

 fluenced in secondary characters by the peculiarity of the 

 female parent. 



205. This should always be borne in mind in procuring new 

 hybrid plants. 



206. Really hybrid plants must not be confounded with such 

 as are spurious, in consequence of their origin being between 

 two varieties of the same species, and not two species of the 

 same genus. 



207." Hybrid plants, although incapable of perpetuation by- 

 seed, are often more abundant flowerers than either parent. 



208. This is, probably, connected with constitutional 

 debility. (162.) ; 



